Generally, a variety of programs (or softwares) are installed in a computer system to drive hardware of a computer such that the hardware and the softwares operate in organic association to execute jobs desired by a user.
During use of a computer, it frequently happens that system data stored in a hard disk is fatally damaged by attack of diverse virus programs or a user's carelessness, mistake, or malicious behaviors. Besides, an unexpected situation or installation or removal of a particular program may cause trouble in the operation of a computer system.
To cope with the above-described problems occurring in a computer system, the following conventional techniques are used to protect data stored in a computer hard disk.
Firstly, a vaccine program is used to protect a computer system from a virus program or to cure a computer system attacked by a virus program. This technique is useful to protect a computer system from already known virus programs but is useless against new virus programs. In addition, even if a virus program has already been known, it frequently happens that system data corrupted by the virus program is not recovered and there is no way but to delete the corrupted system data. Deletion of the system data fatally damages an operating system of the computer, resulting in abnormal operation of the operating system.
Secondly, after programs necessary for a computer system are installed, images in a hard disk is stored in another recording medium (for example, a compact disk-read only memory (CD-ROM)), and the images stored in the recording medium are copied to the hard disk when trouble occurs in the computer system in order to recover corrupted data. According to this technique, a user needs to backup the images stored in the hard disk whenever installing a new program in or deleting a program from the hard disk or recording important data onto the hard disk. A job of backing up the images in the hard disk to another recording medium and recovering the computer system using the backed-up hard disk images requires an extra recording medium and a lot of working time, and it is also very complex.
Thirdly, while the original of a system data is kept in a hard disk as it is, only changed content is stored in a separate system change area. When a wrong change occurs in a system protection area due to a virus program or a user's carelessness, a computer system can be easily recovered by deleting the content stored in the system change area. However, since all data (i.e., both of a used area and an empty area) in the system protection area set by a hard disk dividing unit is protected, a large buffer area (i.e., the system change area) is required to protect the system data. In other words, the size of the buffer area must be the same as that of the system protection area to protect the system data stored in the system protection area without recovery operation. For example, to protect a 120-gigabyte system protection area, a capacity of 120 gigabytes for all system data reflected to the system protection area and additional memory space for other data are required.
Moreover, since the empty area included in the system protection area is also protected, an overload is given to an access to the system data after a hard disk protection program is installed. As a result, the speed of the computer system decreases and the empty area in the system protection area cannot be used at all. In addition, after system recovery, the computer system must be booted in a manager mode and program reinstallation must be performed in order to change a recovery original. Accordingly, it is inconvenient to change the recovery original and it takes a lot of time to create a new recovery original. Besides, if there is an attack of a virus program or a user makes a mistake in installing a program in a state where the computer system has been booted in manager mode to change the recovery original, the computer system cannot be recovered to normal.